1. Field of Invention
The present invention generally relates to sponge surface treatments and more specifically is directed towards a sterile cellular synthetic sponge device made of polyvinyl acetal which has had its surface treated to form a substantially closed surface, retarding tissue ingrowth and also providing a surface layer with reduced wicking.
2. Description of the Prior Art
The literature is replete with references to various types of foam materials including polyurethane, polyisocyanate, polystyrene, polyolefin, polyvinyl chloride, epoxy, urea-formaldehyde, latex, silicone, and fluoropolymer and with methods of controlling the foam or sponge density and other bulk properties during manufacture.
Advances in the development of synthetic polymers have produced radical changes in wound care dressings, bandages, and medical sponges. Factors such as water vapor, oxygen permeability, bacterial impermeability, and selective absorption can be incorporated into new formulations. These new formulations also address specific requirements such as conformability, non-adherence, and adhesiveness. Thus, a family of polymeric products has been formed for wound care including polymeric foams, polymeric films, particulate and fibrous polymers, hydrogels and hydrocolloids.
The optimum wound handling characteristics for wound care dressings and bandages are expressed in general terms such as a) removal of excess exudate and toxic components; b) maintaining a high humidity or moistness at the wound/dressing interface; c) allow gaseous exchange; d) providing thermal insulation; e) protecting against secondary infection; f) freeing the wound from particulate contaminants; and g) removal of the dressing from patient without pain or trauma. Even with the advances in technology, it should be noted that there is no simple dressing or device that can produce the optimum micro environment for all wounds or for all the healing stages of a single wound.
Common factors that impair wound healing include the following:
a). Necrosis, slough and eschar; b) Prolonged inflammation; c) Hypoxemia; d) Vascular insufficiency; e) Protein malnutrition; f) Infection; g) Steriod medications; h) Dehydrated wound bed; and i) Anemia. "How do you score?: Test your skills in Pressure Ulcer Management", p. 197, Joan E. Halpin-Landry, Chronic Wound Care, .COPYRGT.1990.
Sponges and other packing materials used for nasal, sinus or otic packing require a high degree of absorptivity. They normally will swell as body fluids are absorbed. However, current materials and sponges such as porous foams support the coagulated blood and proteins exuding from the cavity surfaces that have been disrupted by surgery or trauma. These coagulated materials enter the pores of the sponge and dry in place. When it is necessary to remove these sponges, they stick to the tissue surface causing pain and occasionally rebleeding.
Thus, there exists the need for a sponge dressing or medical sponge device which has a surface which prevents tissue ingrowth while maintaining the favorable property of absorbing exudate or fluid from the wound area or patient cavity. Another need for such a sponge is that the sponge can swell to provide pressure against the disrupted tissue surface without sticking. Another problem that occurs with a dressing or other medical device inserted in the human body is the mechanical debridement of the wound or cavity caused by firm adhesion of the dressing or device to the wound or cavity because of tissue ingrowth. This adhesion is caused by fibrin produced by the wound or cavity and subsequent spreading of fibroblasts and capillaries.
U.S. Pat. No. 4,997,425 discloses using a porous wound dressing including a first sponge layer for contacting a wound and a second surface remote from a wound. The second surface, the surface remote from the wound, has a pore size smaller than the first surface.
The U.S. Pat. No. 4,054,141 describes a molded absorptive body including an absorptive layer of hydrophilic fibers and a sheath of the hydrophilic fibers bound together by thermoplastic particles. The absorptive body may be provided with a sheath on all sides or only on part of the body. See also U.S. Pat. Nos. 4,381,611; 4,502,156; 4,540,414 and 4,550,725 which show a nonwoven polypropylene fabric in the form of staple or continuous filaments which have been drawn and needled to form a web or batt which is fused on one side. When the fabric is wetted, water is released through the fused side but is not released through the unfused side. Conversely, when the fabric is wetted, the moisture adsorbed on the unfused side migrates or wicks through the fabric toward the fused side. When used as a bandage, the unfused side is in contact with the skin of the wearer.
The U.S. Pat. No. 3,934,587 discloses a solid sheet or film of a polymeric compound containing chemically reactable hydroxyl or amine groups that is reacted in a vapor phase mixture of acid chloride and aldehyde to form a product which is water-repellent on the treated side but water-permeable on the opposite, untreated side. The reactant sheet may be constructed of polyvinyl alcohol.
In addition to the aforenoted references, topical dressings for burn protection used in absorbing necrotic tissues and exudate are shown by U.S. Pat. No. 3,648,692. The dressing of this patent has a thin wound facing layer of dressing constructed of any of a number of various neutral synthetic reticulated open-cell solid foam or sponge materials covered with a barrier membrane. The thickness of the sponge facing layer is noted as being critical (preferably about one-sixteenth of an inch) for positioning of the barrier so that debris, fluids, etc. contained therein are accessible for phagocytic invasion from the body surface. If the layer is too thick, it is noted that segregated exudate located at the interface is not reached by the natural phagocytic action with the undesirable result that infection takes place and spreads within the dressing thereby delaying or preventing the healing process. Another foam sponge product constructed of lyophilized hydrocolloid foam which is capable of absorbing body exudates is shown in U.S. Pat. No. 4,292,972. The wound dressing is preferably constructed of a thin outer oxygen and vapor-permeable film and a layer of an absorbent adhesive such as hydrogel for adhering the wound dressing to the skin and for acting as a reservoir for wound exudate absorbed therein. A layer of collagen, in the form of a sponge or film is adapted for placement directly on the wound, the collagen layer being of smaller dimensions than the absorbent adhesive layer so that areas of the adhesive layer extending beyond the periphery of the collagen layer can be applied to the skin surrounding the wound to adhere the dressing in place.
U.S. Pat. No. 5,009,652 discloses a disposable laminated medical sponge or wipe which has a thin sheet that is impermeable to infectious agents as well as non-wettable by water and a layer of absorbent material having an area which is smaller than that of the impermeable sheet, laminated to the impermeable sheet. The peripheral edges of the absorbent layer are spaced inwardly from the peripheral edges of the impermeable sheet providing a surrounding rim that consists of the impermeable sheet so that liquid which contacts the layer of absorbent material cannot travel through and over the peripheral edge of the impermeable sheet to reach the opposite side of the impermeable sheet.
U.S. Pat. No. 4,967,758 discloses a three layer disposable liner for use with sphygmomanometers. The first layer of the liner is a non-woven web which allows moisture to pass through to a second or middle layer of absorbent material which collects and holds moisture with the third layer being of a thin vapor proof plastic.
U.S. Pat. No. 4,925,453 discloses a medical sponge for use as a wipe to absorb body fluids such as blood which protects the person using the sponge from contact. The sponge is constructed with an absorbent pad covered on one face by a fluid permeable cover sheet and on the other face by a fluid impervious cover sheet, both of the cover sheets enclosing the absorbent pad.
U.S. Pat. No. 4,961,735 discloses a method of using an evaporating bandage which drains body fluids from surgical incisions, wounds and burns. The bandage is constructed with two staggered layers of different woven material. The first layer is made of an absorbent material and the second layer is made of a non-absorbent material.
U.S. Pat. No. 3,900,027 shows a process for making integral absorbent pad bandages from a non-woven thermal plastic fibrous sheet material. The sheet material is compressed in selected portions to reduce thickness and porosity and to limit an absorbent pad having a greater thickness. The resulting sheet material has a plurality of juxtaposed integral absorbent band packages which can be cut off to contain individual bandages. The thermoplastic fibers are noted as being made of any thermal plastic polymeric material which provides differential melting points. During compressing, thickness of the mat is substantially reduced in selected areas in order to reduce porosity and it is noted that the porosity can be totally eliminated. The porosity is reduced in the areas abutting the absorbent pad area so as to limit the spreading of fluids absorbed in the pad section and confine the fluids to that portion. In the course of the compression, the fibers are bonded together due to the thermoplasticity of the fibers by the application of heat and pressure. The fibers can also be bonded and integrated together by the application of a solvent for the fiber polymer prior to the application of pressure.
A burn healing study published in 1962 by Chardack et al. was initiated with the knowledge that pores of an open cell sponge of formalinized polyvinyl alcohol when embedded in living tissues are rapidly permeated by granulation tissue. The clinical experiences of Chardack et al. supported the previous conclusions that an open cell (formalinized).sup.1 polyvinyl alcohol sponge becomes and remains adherent to a denuded body surface, whether the latter has resulted from the excision of integument in clean planes or whether it has been filled in by granulation tissue. The adherence of the sponge is predicated upon proliferation of viable granulation tissue into the pores of the sponge. Adherence was confirmed at the first time check point 24 hours after placement. The material can be repeatedly washed, cleansed and ultimately be replaced by autografts. The Ivalon sponge was being used as a surface for tissue ingrowth in burn victims and the open pores were to be in contact with the tissue. The compressed sponge surface was not identified for prevention of tissue ingrowth or reduced tissue shear upon removal of a treated nasal packing. Synthetic Substitutes For Skin, Chardack et al. Plastic & Reconstructive Surgery, Vol. 30, No. 5 (November 1962). FNT .sup.1 added for edification